Carrier telegraph circuits



Sept. 1, 1925. 1,551,559 I B. P. HAMILTON CARRIER TELEGRAPH CIRCUITS Filed Oct. 2%, 1 0

INVENTOR ATTORNEY Patented Sept. 1, 1925.

UNITED STATES PATENTO F-ma BAXTER 2. Emma, or BROOKLYN, NEW Your, assmnoa TO annnrcan TELE- rnonnnnn TELEGRAPH oomuuw, A conronsrron or new, YORK.

alumina 'rnmcmrn omcurrs.

Apglicatlon and October 21, 1920. s mi 110,418,484.

To all whom it mag concern:

Be it known that I, BAXTER P. HAMIL'roN, residing at Brooklyn, in the county of Kings and State of New York, have invented certain Improvements in Carrier Telegraph Circuits, of which the following is a specification.

This invention relates to signaling systems and, more particularly, 'to signaling systems in which telegraph signals may be transmitted by means of carrier currents.

One of the objects of the invention is to provide an arrangement whereby an ordinary subscribers circuit orloopof a telegraph system may be associated with the channels of a multiplex system. A further object of the invention is to provide arrangements in a system of the character ust described, whereby, in two-way transmission of telegraph signals, the received signals will not react upon the transmitting apparatus so as to be transmitted back in the direction from which they originated.

Other and further objects of the invention will be clear from the following description, when read in connection with the accompanying drawing, Figure lot which is a circuit diagram of one form of the invention and Fig. 2 of which is a circuit dia ram of a modified form of the invention.

Referring to Fig 1, ML designates amaiu transmission line over which two-way transmission may take place by means of carrier currents. be impressed upon the line LM, by means of a carrier transmitting circuit TL, while received transmission may be taken from the line ML through carrier receiving circuit RL. In order .to render the circuits RL and TL substantially conjugate, the circuit BL is associated with the main line ML through a well-known form of' balanced transformer 10, and an artificial line or network MN is provided for balancing the main line ML.

As many carrier channels as desired.

may be associated with the circuits TL and RL through tuned circuits, in a well-known manner. For purposes of illustration, but one channel is shown associated with each circuit, it being understood, however, that in practice additional channels may be provided. The transmitting channel illustrated is associated with the common transerator Outgoing transmission may lations from the generator G.

mitting circuit TL through a tuned circuit arrangement TF and comprises a vacuum tube am(plifier TA and a vacuum tube gen- The receiving channel is associated with the common receiving circuit RL through a similar tuned circuit arrangement RF and includes a vacuum tube detector D and a receiving relay R. A subscribers loop L, including a key K and sounder S, is provided, and the circuit of the subscribers loop is controlled by means of a repeating relay 11, controlled by the receiving relay B, so that received signals may be repeated from the receiving carrier channel of the subscribers loop. A central oifice sounder S is also controlled by the repeating relay 11. A transmitting relay T is included in the subscribers loop, saidtransmitting relay being in series with the relay 11, which controls a monitoring sounder S" at the central office, so that telegraph signals originating in, the loop will be indicated-by said sounder; A transmitting key K" may be also provided in the transmitting portion of the loop at the central oflice. The contacts of the sounder S are arranged to short-circuitthe contacts to the receiving relay R when signals are being transmitted, in order that if the receiving operator desires to break in, the received signals cannot be repeated to the loop while the break signal is being transmitted. A condenser O is associated with the'transmittingrelay T and is controlled by contacts of the repeating relay 11, for the purpose of momentarilyholding the transmitting relay energized while the armature of the repeating relay 11 is operating in response to. received signals, thus preventing the received signals from being repeated back to the carrier circuit by the transmitting relay T. The transmitting relay T controls a circuit 13 for short-circuiting the input circuit of the amplifier TA, thereby preventing the transmission of oscil- The operation is as follows: Normally, when signals are not being transmitted, the carrier frequency of the channel is sent out with uniform amplitude. Consequently the frequency assigned to the receiving channel will be received from the main line in the circuit RL and selected by the tuned circuit arrangement RF to be impressed upon the detector D, thereby causing a steady direct 'B through the winding of the relay 11. Re-

lay 11 holds the circuit of the subscribers 100 11 normally closed over a circuit from positive battery through the sounder S over a key K, front contact of relay 11, through the winding of relay 12, over key K and ing relay 11.

through the winding of transmitting relay T to negative battery. The sounder S, relay 12, and transmitting relay T, are, therefore, energized.

With the circuit in the condition just de scribed, the operator of the loop circuit may transmit signals by opening the key K or the operator at the central olfice may transmit by opening the key K. In either case, the sounder S, relay 12, in transmitting relay T, will be de-energized. The rela T, which normally holds open the contro ling circuit 13, upon being energized, closes said circuit to short-circuit the input circuit of the amplifier TA. With the circuit 13 open,

the generator Gr generates oscillations which are impressed upon the input circuit of the amplifier TA and after being amplified, are transmitted through the tuned circuit TF and over the circuit TL to the main line ML. Upon closing the circuit 13, however, a path for the high frequency generated by the generator G is provided through the condenser 14 to ground, so that substantially no carrier currents are transmitted through the amplifier TA. The interruptions of the transmission of the carrier frequency operate the receiving apparatus at the distant end of the line ML. The deenergization of relay 12, in the meantime, opens the circuit of the central otfice sounder S which, in turn, over its back contact, short-circuits the contacts of the receiving relay R.

Should an operator at the distant end of the main line interrupt the carrier frequency transmitted to the receiving channel, the direct current from the relay R will be interrupted and the relay de-energized, thereby opening the circuit of the repeat- The de-energizat-ion of the repeating relay opens the circuit of the sounder S and also opens the circuit of the loop L through the sounder S, relay 12, and transmitting relay T. The sounder S consequently registers the signal at the loop operator?s station. In the normal closed condition of the loop, the condenser C acquires a charge. When, however, the loop is shiftin opened by the de-energization of the repeating relay 11, the condenser C discharges through the windings of the relay l2 and the transmitting relay T, during the moment that the armature of the relay 11 is from its front to its back contact. This discharge holds the relay 12 and the transmitting relay T energized until the armature of the relay 11 rests upon its back contact, when the holding circuit for said relays is provided from ground over the back contact of the relay 11, through the Winding of the relay 12 over key K and through the winding of the relay 12 over key K and through the winding of relay '1 to negative battery. The relay 12 and the transmitting relay T do not, therefore, respond to the opening of the loop circuit at the repeating relay 11, and the received signal is not transmitted back over the transmitting carrier channel to the line ML. At the end of the interruption of the received frequency just described, current again flows through the receiving relay R, closing the circuit of the repeating relay 11, which again closes the loop. The condenser C, which has again acquired a charge, discharges through the winding of the relay 12 and the transmitting relay T, to hold said relays energized, while the armature of the repeating relay moves from its back to its front contact.

If, while signals are being received, it should be desired to interrupt the sending operator, in order to transmit in the opposite direction, a break signal may be transmitted by holding open the key K or the key K. This results in the de-energization of the relay 12 and the transmitting relay T. The transmitting relay T, by closing the circuit 13, interrupts the transmission of the carrier frequency to the distant station, while the relay 12 opens the circuit of sounder S" which, in turn, at its back contact, short-circuits the contacts of the receivin relay B, so that the repeating relay 11 is eld energized and the received signals cannot be repeated to the loop L.

The effect of the break signal at the distant station ma be understood from a consideration of the effect of a break signal transmitted from the distant station to the receiving circuit illustrated. During the break, the carrier frequency is not transmitted to the detector D- and, consequently, no current flows through the relay R,Wl1lCl1 is de-energized and holds open its contacts. Should the operator at this moment have the key K or the key K open for the transmission of a space signal, the relay 12 will be de-energize'd and, consequently, the sounder S will, at the moment, provide a locking circuit for the relay 11. As soon, however, as one of the keys in the loop is closed to transmit a dash or a dot, the relay 11 is again ener ized and the sounder S opens the short circuit about the contacts of the receiving relay R. The relay v11 is at once deenergized and opens the loop circuit in the manner already described, at the same time locking up the relay 12 and the transmitting relay T, over the back contact of relay 11. The sounder S" is, therefore,

held energized to maintain the shunt circuit about the receiving contacts of the relay .R open.

The conditions just described obtain as long as the break signal is being transmitted. The operatorwho' is transmitting by means of the key K, will at once recognize that a break signal is being received, by reason of the fact that the sounder S no longer .responds to the actuation of the key K, since the loop circuit is held open. The operator will, therefore, close the key K and the operator who is breaking in will, after transmitting the break signal a short interval, begin to send in the regular manner, whereupon the circuit illustrated functions to receive in the manner already described.

A somewhat similar arrangement is illustrated in Fig. 2, differing from that of Fig. 1 however, in that, instead ofthe condenser discharge arrangement for holding the relay 12 and the transmitting relay T, a magnetic locking feature is provided. For this purpose, the relay 12, instead of being provided with a single coil, as in Fig. 1, is provided with a main coil 12', which is included in the loop circuit,'and an auxiliary coil 12', which is controlled by the repeating relay 11, the coil 12 acting as a holding coil. The circuit of the loop. does not, in this instance, include the transmitting relay T, but passes only through the coil 12 of the relay 12 andthe key K. The transmitting relay T is arranged in a local circuit controlled by therelay 12. The receiving sounder S is also arranged in a slightly different manner, being connected in series with the relay 11, instead of being in a local circuit controlled by said relay.

The operation is as follows: Repeater relay 11 and sounder S are normally energized as before. The relay 11 at one of its front contacts, short-circuits the coil 12" of the relay 12, so that said coil is de-energized. The relay 11 holds the loop circuit L closed over'the circuit as follows: from battery to the sounder S, key K, front contact of relay 11 and the coil 12' of the relay 12. The coil 12' of the relay 12 holds the armature of said relay attracted so that the circuits of the transmitting relay T and of the transmitting sounder S are closed. Upon opening the loop circuit by means of the key K or the key K, the coil 12 is deenergized and the armature of the relay 12 falls off, so that the transmitting relay. T is deenergized to interrupt the gtransmission of the transmitting rey, the circuit will be restored to its original condition and the carrier frequency again transmitted.

Interruptions of the received carrier frequency cause the de-energization of the receiving relay R. The circuit of the repeatmg relay 11 and the sounder S are opened and the relay 11 opens the circuit of the loop, including the circuit of the coil 12 of the relay 12. The short-circuit about coil 12" is removed, at the same time, however, so that the relay 12 is maintained energized during the interruptions of the loop circuit and the received signals cannot be transmitted back to the main line ML by the operation of the transmitting relay T.

If, while signals are being received, the operator at the loop position desires to interrupt or break in, the key K may be opened. This is without effect if the receiving relay is de-energized at that moment, but as soon as the receiving relay is again energized to short-circuit the coil 12", the armature of therelay 12 will fall off, since both coils 12' and, 12 are de-energized. The transmitting relay T and the sounder S" are de-energized, the transmitter'functioning to interrupt the transmitting frequency While the sounder S" short-circuits the contacts of the receiving relay R and holds the sounder S and the repeating relay 11 energized as long as the break signal continues. The received signals, therefore, are not repeated to the loop during the continuance of the break.

The effect of a break signal received from the distant station is to cause the de-energization of the receiving relayR during the continuance of the break. If, at this moment, the loop L is opened for the transmission of a space signal, the sounder S will be de-energized and the de-ener'gization of the relay R will be without effect.- As soon, however, as the key in the loop is again closed to transmit a dot or a dash, the coil 12 is energized to close the circuits of the transmitting relay T and sounder S5, consequently, the sounder S removes the short circuit from about the contacts of the relay R and the repeating relay 11 is at once de-energized to open the loop circuit. The deenergization of the relay 11, by removing the short-circuit from the coil 12" causes the energization of said coil and further interrupt-ion of the loop by means of the key K or the keyK is without effect, since the relay 12 remains energized to hold the sounder S" energized, thereby preventing any possibility of short-circuiting the con tacts of the relay R, and the opening of the loop by means of the relay 11, prevents the sounder S from responding to the trans mitted signals. The operator atthe loop, by observing that the sounder no longer follows the transmitting key, knows at once that a break signal is being transmitted.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated, without departing from the spirit of the invention, as defined in the following claims.

What is claimed is:

1. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a low frequency direct current telegraph circuit, a transmitting relay associated with said circuit and arranged to con trol said carrier transmitting channel, a receiving relay associated with said carrier receiving channel and arranged to control said telegraph circuit, and means to prevent said transmitting relay from respondin; to signals received by said receiving relay.

2. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a direct current telegraph circuit, a transmitting relay associated with said telegraph circuit and responding to changes in the condition of said circuit to control said transmitting channel, a receiving relay as sociated with said receiving channel and responding to signals received by said channel to produce changes in said telegraph circuit similar to those actuating the transmitting relay, and means for preventing said transmitting relay from being actuated by said receiving relay.

3. In a signaling system, a carrier line, a

carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a direct current telegraph circuit, a trans mitting relay associated with said telegraph circuit and operating in response to changes from current to no current condition in said circuit, and vice versa, to control said transmitting channel, and a receiving relay associated with said receiving channel and operating in response to signals received in said channel to produce in said telegraph circuit changes from current to no current condition and vice versa, and means to pre-. vent said transmitting relay from being actuated by said receiving relay.

4. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a direct current telegraph circuit, a transmitting relay associated with said telegraph circuit and operating in response to makes and breaks of said circuit to control said transmitting channel, a receiving relay associated with said receiving channel and operating in response to signals received in said channels to produce makes and breaks in said telegraph circuit, and means for preventing said transmitting relay from responding to the action of said receiving relay.

5. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a direct current transmitting relay associated with a telegraph circuit and responsive to current changes in said tel egraph circuit to control said transmitting channel, a receiving relay associated with said receiving channel and responsive to signals received in said channel to produce ourrent changes in a telegraph circuit similar to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a transmitting relay associated with a telegraph circuit and responsive to changes from current to no current condition in said circuit and vice versa, to control said transmitting circuit, a receiving relay associated with said receiving channel and responsive to signals received in said channel to produce changes from current to no current condition and vice versa, in a telegraph circuit.

7. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, means to render said transmitting and receiving channels substantially conjugate with respect to each other, a transmitting relay associated with a telegraph circuit and responsive to makes and breaks in said circuit for controlling said transmitting channel, a receiving relay associated with said receiving channel and responsive to signals received in said channel for producing makes and breaks in a telegraph circuit.

8. In a signaling system, a carrierline, a carrier transmitting channel to transmit nals transmitted over said circuit to control said transmitting channel, a receiving relay associated with said receiving channel and responsive to signals received in said channel to control said telegraph circuit, and

means whereby when said transmitting relay 1S actuated the receiving relay is prevented from controlling said telegraph cir-.

cuit.

9. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, a direct current telegra h circuit, a transmitting relay associate with said telegraph circuit and responsive to changes from current to no current condition in said circuit and vice versa to control said transmitting channel, a receiving relay associated with said receiving channel and responsive to signals received in said channel to produce changes from current to no current condition and vice versa in said telegraph circuit, and means whereby when said transmitting relay is actuated said receiving relay is prevented from producing changes in said telegraphcircuit similar to those actuating the transmitting relay.

10. In a signal system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, a-direct current telegraph circuit, a transmitting relay associated with said circuit and responsive to makes and breaks in said circuit to control said transmitting channel, a receiving relay associated with said receiving channel and responsive to signals received in said channel to produce makes telegraph circuit, means to prevent said ,receivii'ig relay from producing makes and breaks in said telegraph circuit when said transmitting relay is actuated.

11. In a signaling system, a carrier line, a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, a direct current telegraph circuit, a transmitting relag associ-. ate with said telegraph circuit an responsive to signals transmitted over said circuit to control said carrier transmitting channel, a. receiving relay associated with said receiving received said telegraph circuit, and means operative when said transmitting rela responds a signal transmitted over sai telegraph cirand breaks in said.

channel and responsive to signals 'in said channel to transmit overcuit to short-circuit the contacts of said a receiving relay. 12. In a signaling system,.a carrier hne,

'a carrier transmitting channel to transmit over said line, a carrier receiving channel to receive from said line, a direct current telegraph circuit, a transmitting relay associated with said telegraph circuit and responsive to signals transmitted over said circuit to control said transmitting channel a receiving relay associated with said receiving channel and. responsive to signals received in said channel for transmitting signals to said telegraph circuit, and means whereby said transmitting relay is prevented from respondingto signals attempted to be transmitted over said telegraph circuit when a continuous break signal is' received in said carrier receiving channel.

13. In a signaling system a carrier transmitting channel, channel for translating low frequency signals into carrier currents, said means including a vacuum tube oscillator for supplying the carrier frequency tube for controlling the transmission of the carrier, frequency from the oscillator to the line, together with the action of said last mentioned vacuum tube in accordance with telegraph signals, a low frequency telegraph circuit and a mechanical telegraph repeater for repeating telegraph signals from said low frequency telegraph circuit to said carrier transm tting channel to control the operation of said last mentioned vacuum tube. y 14:. In a signaling system, a carrier line, a carrier transmittin channel to transmit over said line, inclu ing means for translating -low frequency signals to carrier currents, a carrier receiving channel to receive from said line including means for translating carrier currents into low frequency signals, means to render. said transmitting and receiving channels substantially conjugate with respect to each other, a low frequency direct current telegraph circuit and a mechanicaltwo-way telegraph repeater for associating said telegraph circuit with said transmitting and receiving channels, whereby low frequency telegraph signals may be re ated from said telegraph circuit to sai transmittingchannel and whereb carrier signals received in said receiving 0 annel may be repeated as low frequency si als to said telegraph circuit.

ii testimon whereof, I have signed my name to this specification this 18th day of October, 1920.

BAXTER r. HAMILTON.

means for determining means associated with said and a vacuum I 

